In U.S. Pat. No. 4,079,821, there is disclosed an electromagnetic clutch of the type having an axially movable armature which is drawn into and out of frictional engagement with an inner body by the action of an electromagnetic coil, which engagement serves to establish drive through the clutch. This particular clutch design incorporates a torque boosting arrangement consisting of a plurality of balls disposed between the armature member and the output (or input) drive member with a series of conical pockets formed in the respective armature and drive members, which serves to increase the speed of engagement and the torque capacity of the clutch upon axial movement of the armature into engagement with the inner body, as described in detail in that patent. This clutch operates in a highly advantageous manner in that it exhibits a relatively high torque capacity.
Some applications, however, require a relatively light weight clutch. In the particular design disclosed in that patent, the elements are relatively massive, being formed of machined steel components. In addition, the extremely rapid action of the clutch by virtue of the torque booster feature in some applications requires a shock absorbing feature built into the clutch in order to protect the output shaft from the shock of the sudden engagement of the clutch and/or sudden increases in torque.
One arrangement for providing a shock absorbing action in such clutches has been by the interposing in the drive of a torsional resilient mass of material having suitable resilient shock absorbing characteristics, such as an elastomeric ring which serves to minimize the transmission of torsional shocks.
It is, accordingly, an object of the present invention, to provide an electromagnetic clutch of the design disclosed in U.S. Pat. No. 4,079,821, of a relatively light weight configuration.
It is yet another object of the present invention to provide a clutch of the type described in which a shock absorbing feature is provided which acts in cooperation with the torque booster arrangement to reduce sudden shock loadings.